British Airways tonight threatened to suspend co-operation with Britain's largest trade union after last-ditch talks failed to prevent a three-day strike by cabin crew starting today.

In a dramatic escalation of the bitter industrial dispute with Unite, BA warned that it will scrap an agreement that gives shop stewards the use of company offices and time off to represent members – unless a new framework is drawn up.

One industrial relations expert said that ending the arrangement, which stipulates how much work BA employees can do for Unite and what facilities they use, would reduce co-operation to the "bare minimum".

The failure of the peace talks is a bitter blow to Gordon Brown, who was desperate to banish the spectre of large-scale industrial action 46 days before the likely election date.

Tonight an extensive strike-breaking plan moved into gear at BA as the airline prepared to move 65% of its passengers over the next three days with a workforce of 1,000 volunteer cabin crew and 22 chartered jets, including three Ryanair planes complete with no-frills flight attendants.

Millions of Britons face transport disruption in the run-up to Easter, after signallers at Network Rail voted to strike in a move that could see them join a walkout with thousands of maintenance workers over the bank holiday.

BA cabin crew have also called a further, four-day strike from 27 March if there is still no agreement by the end of next week. The first BA cabin crew strike since 1997 begins tomorrow morning after talks between Willie Walsh, BA chief executive, and Tony Woodley, joint general secretary of Unite, collapsed in acrimony this afternoon. The dispute centres on BA's decision to unilaterally cut staffing levels on every flight by at least one crew member.

Citing Walsh's request for a "radical, far-reaching review" of BA's relationship with Unite, Woodley warned that BA was bent on breaking trade unionism's grip on the airline. "BA does not want to negotiate and ultimately wants to go to war with this union," he said. And in a letter to Woodley outlining a formal peace offer, Walsh stepped up the pressure by saying he would scrap the facilities agreement that regulates BA's relationship with Unite if the union does not renegotiate its relationship with the carrier by 18 June.

Marc Meryon, industrial relations partner at Bircham Dyson Bell, said: "It is effectively holding a gun to the union's head and saying, unless you reach a deal on reworking this relationship we are going to walk away from it."

Meryon said BA would struggle to derecognise Unite, which represents 12,000 BA cabin crew, because of its size.

Walsh said: "It is deeply regrettable that a proposal I have tabled to Unite, which I believe is fair and sensible and addresses all the concerns of cabin crew, has not been accepted.The offer remains available, but it will be withdrawn once industrial action commences. Tens of thousands of BA people now stand ready to serve our customers. BA will be flying tomorrow and will continue to fly through these periods of industrial action."

A No 10 spokesman said: "The prime minister believes that this strike is in no one's interest and will cause unacceptable inconvenience to passengers. He urges the strike be called off immediately. He also urges BA's management and workforce to get together without delay to resolve what is a dispute about jobs and wages."

The talks breakdown was pounced on by the Conservative party, which has sought to make political capital out of the funding links between Labour and Unite, one of the party's biggest donors.

"Labour's union paymasters at Unite are determined to inflict travel misery on thousands of families," said Theresa Villiers, the shadow transport secretary.

Preparations were under way tonight to have picket lines at seven points around Heathrow. Under an agreement with BAA, the airport's owner, striking cabin crew will not be allowed to protest directly outside airport terminals.

A BA spokeswoman said the 30,000 daily passengers unable to travel due to the strike – around 45,000 will be able to travel – were almost certain to have made alternative plans. "We don't expect vast numbers of disgruntled people because we put our revised schedule out on Monday. We have also been contacting them proactively through email."